A process of adding a hydrogen halide to a compound containing an olefinic linkage



Patented a. 27, 1936 UNITED STATES A PROCESS BALID OF ADDING A HYDROGENE TO A COMPOUND CONTAINING AN OLEFINIC LINKAGE Morris 8. Kharasch,Chicago, 111., assignor to E. L du Pont de Nemonrs 8; Company,Wilmington, DeL, a corporation of Delaware No Drawing.

Application December 16, 1933, Serial No. 702,793

11 Claims. (Cl. 260-182) This invention relates to a process of addinghydrohalogens to oleflne hydrocarbons and their derivatives, and moreparticularly it relates to a method for controlling the reaction toproduce addition products of a predetermined character.

Reactions involving an olefine and a hydrogen halide are ingeneralwell-known to the art but investigators, in carrying 'out reactions ofthis type, have discovered either that a reaction involving an oleflneand a given hydrohalide will result in a mixture of isomers or that thereaction '-will yield one-isomer to the practical exclusion of another.In addition, reactions involving the same hydrocarbon and the samehydrogen halide, 15 .even when carried out under the same generalconditions, yield reaction mixtures of widely diverse character, thatis, a reaction carried on at one time may produce one isomerexclusively, while another time it may yield a mixture containing morethan one isomer in substantial amounts. Many estimates have been madeand much research has been done with a view to solving the discrepanciesreferred to but no theory has as yet been devised which would enable oneto predict with exactness the composition of a product to be obtained.

In addition, in many reactions of this character where one isomer may bedesired, for some reason unaccountable to the art, it has beenimpossible to produce the desired isomer, either quantitatively or inany desired amount. The present invention concerns itself with a methodfor controlling the reaction between oleflnes and hydrogen halides toproduce, with uniformity,

halogen derivatives of a predetermined character. One object of thepresent invention comprises the control of reactions involving theaddition of hydrogen halides to olefines to produce a given additionproduct. A further object of the inven- 40 tion comprises the control ofreactions of this type to yield a given product in substantiallyquantitative amounts. A further object of the invention comprisesreacting a hydrogen halide and the olefine in the presence of anantioxidant.

Further objects of the invention will become apparent from the followingdescription of the inventlon.

It has now been found that the addition of hydrogen halides to olefinesor halogenated olefines may be controlled by the use of antioxidants.

The addition of hydrogen halides to the double bond of an oleflnehydrocarbon or a substituted oleiine hydrocarbon containing anunsaturated bond, will occur in the absence of antioxidants,

but wheredifferent sources of olefine are used the results and thecharacter of the reaction products will show a wide lack of uniformity.

Furthermore the reaction carried out in the absence of an antioxidantwill yield either one isomer to the practical exclusion of another or 5will produce an isomer different from that produced predominately if anantioxidant is used. In any event the effect of the presence of theantioxidant is to produce one type of isomer while the efiect of notusing an antioxidant is to favor the 10 production of a differentisomer. It is believed that the reason for this difference in resultslies in the fact that the presence of peroxides or hy droperoxides playsan important part in the character of the isomer produced and thiseffect can be either controlled or eliminated by the use ofantioxidants. Oxygen may be found to give results resembling thoseobtained in the presence of peroxides, owing to its ability to formperoxides with many olefines. The fact that its eflect is a re- 20 sultof a peroxide formation is shown by the fact that the olefines may beexposed to oxygen for a suitable period and then the free oxygencompletely removed by distillation in vacuo leaving 25 only that oxygenwhich is combined as peroxides of the olefine and the reaction willprogress as though the oxygen were present. The foliowing examples,which are to be construed as illustrative only, represent various formsof applying 30 the invention.

Example 1 Example 2 One mol. of propylene, 1.23 mols of hydrogen 4bromide, 0.05 mol. of thiocresol and 0.0001 moi. of manganese chloridewere sealed in an air-tight pressure vessel in the complete absence ofair and allowed to stand at room temperature for 18 50 hours. At the endof this period, the vessel was opened and the products were isolated byfractionation. It was found that a yield of propyl bromide had beenobtained and the product was isopropyl bromide. 55

Example 3 of propyl bromides, but only 79% of the product was theisopropyl isomer.

Example 4 In the manner described in Example 2, 1 rnol.

or propylene and 1.23 mole of hydrogen bromide were reacted, but in thiscase the antioxidant mixture (thiocresol and manganese chloride) wasomitted and instead there was added 0.041 moi. of benzoyl peroxide.Isolation of the product showed a yield of over 87% of n-propyl bromide.

Example 5 Example e was repeated, allowing air to be enclosed in thevessel with the reactants and the product was over 96% n-propyl bromide.

Example 6 (inc moi. of propylene, 1.23 mois. of hydrogen bromide and0.13 moi. of ascaridole were enclosed in an air-tight vessel and held at-78 for 32 minutes. Isolation of the product gave a good yield of propylbromides which proved to be 100% n-propyl bromide, the isopropyl isomerbeing absent.

The above six examples demonstrate the manner in which the addition ofhydrogen bromide may be controlled to yield either iso-propyl bromide inthe absence of peroxides, or n-propyl bromide in the presence ofperoxides.

Example- 9 One moi. of pure aliyi bromide was sealed in a reactionvessel in the dark and in the absence of air with 1.5 mole of hydrogenbromide and 0.11 mol. of diph'enyi amine. After reacting for ll days, a97.5% yield of bromides was obtained which proved to be over 89% pure,1,2-dibromopropane.

Ewcmple 8 Repeating Example 7 but omitting the antioxidant, diphenylamine and substituting 0.023 moi. of benzoyl peroxide, the reaction gavea 95.4% yield in 18 hours, of which less than 18% was1,2-dibromopropane, over 82% of the product being 1,3-dibromopropane.

The examples illustrate that the reaction of addition of hydrogenhalides to double bonds of olefines and oieflnic derivatives may becontrolled by the presence or absence or antioxidants. In some cases thenormal reaction is a reaction which takes place in the presence oi anantioxidant or to put; it difierently, in the absence of peroxides orhydroperoxides. In other cases the better known reaction is that whichtakes place in the presence of a peroxide but regardless of the natureof the normal reaction, the character oi the reaction products will beinfluenced by either diminishing or limiting any peroxide which may bepresent.

It will be understood that the amount of antioxident to be added will bevaried according to the product desired and the character of theantioxidant, and that by such variation a wide variety of products maybe produced, including not only single itomers, but also mixtures ofisomers.

Antioxidants suitable for use in the practice of the invention are thosecompounds recognized as being efiective to prevent the atmosphericoxida- 5 tion of rubber, fats and oils. The term "antloxident" will beconstrued throughout the specification and claims to include thesesubstances which act to eliminate the peroxides or conditions favoringthe formation of peroxides as cat- 10 alysts. Thus antioxidants are anymaterials which may be added and by their presence permit the samereactions to be carried out in air or in the presence of peroxides whichwould otherwise be obtained only in the absence of air and 15 peroxides.

Antioxidants which are suitable for the practics of the invention aresuch as: the usually accepted rubber antioxidants, also diphenylamine,hydroquincne, catechol, pyrogallol, other polyhydroxy phenols,carvacrol, cresol, dibutylamine, phenyl-a-naphthylamine, thiophenols,thiocresol, thioplienols in conjunction with manganese salts,phenyi=b-naphthylamine, tertiary butyl isocyanide, dimethylaniline,mercaptobenzo thiazole, monoand dibenzylamincphenoi, and other compoundswell known for the prevention of atmospheric oxidation of rubber, fatsand oils. The more powerful the antioxidant the higher the yield of theproducts, the formation of which the antioxidant favors, thusdiphenylamine and phenylnaphthylamine are quiteefiective but the sulfurcontaining antioxidants, particularly thicphenol and thiocresoi areexceedingly powerful.

It is believed that the sheet of peroxides upon 85 the manner ofaddition of hydrohalogens involves the intermediate formation of aperoxide to carry the reaction in a particular manner, and converselythe efiectiveness of any antioxidant in overcoming the efi'ect of theperoxide, is in part 40 dependent upon the ease of formation ofperoxides of the olefine. Thus some oleilnes or their derivatives, suchas vinyl bromide, are so sensitive to traces of peroxides that anantioxidant which would be satisfactory in a given concentration inanother olefine might appear to be almost without efiect in thisparticular case.

It has been also found that other experimental conditions, such assurface, temperature, pressure, light and radiation by activating wavesmay have a secondary influence upon the course of these reactions, butonly insofar as they eflect the activity of the peroxides orantioxidants present', or upon the reactions which they catalyze. Thusin the addition of HBr to aliyl bromide, the peroxide catalyzed reactionresulting in the formationoi' the 1,3-dibromoproduct has a very muchgreater temperature coemcient than the uncatalyzed reaction, thereforeat high temperatures, a very little peroxide is capable of 80 bringingabout a 100% yield of the 1,3-addition, whereas at low temperature thereaction becomes very slow and further, the velocity of the catalyzedreaction is disproportionately decreased and appreciable amounts of theuncatalyzed product (the 1,2-dibromopropane) may appear even in thepresence of the catalyst. Likewise, in the addition of 1-13! to ally]bromide, radiation with infra-red is without eflect upon the uncatalyzedreaction, except that the velocity oi the reaction is increased, and inthe presence of antioxidants, the reaction in the presence of infra-redradiation is identical with that observed in the dark, but in thecatalyzed reaction,

the peroxide is greatly activated and the cata-l time tremendouslyaccelerat s the speed of lyzed reaction is promoted, resulting ingreater speed of addition and higher yields of the catalyzed product,the 1,3-dibromopropane. In the same manner, solvents may assist theperoxides in activating the catalyzed reaction, or promote theeffectiveness of the antioxidants in disposing of peroxides. In no caseyet observed however does the solvent as such, effect the direction ofthe reaction, except insofar as it, itself, may form peroxides, or maybe an antioxidant. Thus, ligroin when allowed an opportunity to oxidize,may form traces of peroxides which are somewhat eifective in bringingabout the peroxide be.- havior and on the other hand tertiary butylisocyanide is a weak antioxidant and at the same reaction. Acetic acidor other acids such as phenylacetic, propionic, etc., may act asantioxidants, not per se, but because they possess the ability todecompose peroxides.

The invention is applicable to reactions involving hydrohalides ingeneral and particularly hydrogen chloride and hydrogen bromide, whileany of the olefines or substituted olefines may be used. Toindicate thewide application of the invention-it includes, for example, reactionsbetween any of the hydrohalogens and propylene,

allyl chloride, vinyl bromide, vinyl chloride and any of the otheroleflnes and substituted oleflnes. In the application of theseprinciples to the addition of hydrogen iodide to olefines, it has beenfound that the hydrogen iodide itself is sufllci ently powerful reducingagent to destroy the peroxides present and, therefore, generally resultsin the reaction which is characteristic in the absence of peroxides. Ingeneral then it may be said that the process of this invention isapplicable to any reaction involving the addition of the hydrogen halideto a compound containing olefinic unsaturation.

.Thus it is obvious that by the practice of this invention certainmarked advantages are obtainable. It is not only possible to prepare agiven compound or mixture of compounds as de- I bodiments of thisinvention may be made without departing from the spirit and scopethereof and it is not intended to be limited except as indicated in theappended claims.

I claim:

1. In the process of controlling the adding of hydrogen halide to acompound taken from the class consisting of mono-oleiine hydrocarbonsand halogen substituted mono-oleflne hydrocarbons so as to form inpredominating amount a desired isomer, the step which comprises addingto the reaction mass an antioxidant per se.

2. In the process of controlling the adding of a hydrogen halide to amono-oleflne hydrocarbon so as to form, in predominating amount adesired isomer, the step which comprises adding to the reaction mass anantioxidant per se.

3. In the process of controlling the adding of a hydrogen halide to amono-oleflne hydrocarbon in the presence of a solvent so as to form inpredominating amount a desired isomer, the step which comprises addingto the reaction mass an antioxidant per se.

4. The process of controlling the adding a hydrogen halide to anoleiinic linkage of a compound taken from the class consisting ofmonooleflne hydrocarbons and halogen substituted mono-oleflnehydrocarbons so as to form in predominating amount a desired isomerwhich comprises carrying out the reaction in the presence of a solventwhich is also an antioxidant per se.

5 In the process of controlling the adding of a hydrogen halide to acompound taken from the class consisting of olefinic hydrocarbons andhalogen substituted oleflne hydrocarbons so as to form in predominatingamount a desired isomer, the step which comprises adding to the reactionmass an antioxidant taken from the class consisting of diphenylamine andphenylnaphthylamine.

6. In the process of controlling the adding of hydrogen bromide to acompound taken from the class consisting of aliphatic hydrocarbonscontaining one alpha olefinic linkage and their halogen substitutedoleflne products so as to form in predominating amount a desired isomer,the step which comprises adding to the reaction mass an antioxidant perse. r l

7. In the process of controlling the adding of hydrogen bromide to acompound taken from the class consisting of aliphatic hydrocarbonscontaining one alpha olefinio linkage and their halogen substitutedolefine products in the presence of a solvent so as to form inpredominating amount a desired isomer, the step which comprises addingto the reaction mass an antioxidant per se.

8. The process of controlling the adding of hydrogen bromide to anoleflnic linkage of a compound taken from the class consisting ofaliphatic hydrocarbons containing one alpha olefinic linkage and theirhalogen substituted olefine products so as to form in predominatingamount a desired isomer, which comprises carrying out the reaction inthe presence of a solvent which is also an antioxidant per se.

9. In the process of controlling the adding of hydrogen bromide to acompound taken from the class consisting of aliphatic hydrocarbonscontaining an alpha olefinic linkage and their halogen substitutedolefine products so as to form in predominating amount a desired isomer,the step which comprises adding to the reaction mass an antioxidanttaken from the class consisting of diphenylamine andphenylnaphthylamine.

10. In the process of controlling the adding of a hydrogen halide to acompound taken from the class consisting of oleflnic hydrocarbons andhalogen substituted olefine hydrocarbons so as to form in predominatingamount a desired isomer, the step which comprises adding to the reactionmass an antioxidant taken from the class consisting of thiophenol andthiocresol.

11. In the process of controlling the adding of hydrogen bromide to acompound taken from the class consisting of aliphatic hydrocarbonscontaining an alpha oleilnic linkage and their halogen substitutedoleflne products so as to form in predominating amount a desired isomer.the step which comprises adding to the reaction mass an antioxidanttaken from the class consisting of thiophenol and thiocresol.

MORRIS S. KHARASCH.

